1. Field of the Invention
The present invention relates to an oil channel structure extending to a hydraulic actuator in an automatic transmission, specifically to an oil channel structure for oil supply through a slanted oil channel from a supply oil channel formed in a stationary member such as a casing to a rotating hydraulic actuator.
2. Description of the Prior Art
Generally, in an automatic transmission as shown in FIG. 5 in which a hub 103 is rotatably mounted on a boss section 102 extending from a casing, a one-way clutch F is mounted on the hub 103, and a clutch drum 110 is fixed to form a hydraulic actuator 105 comprising a piston 111 for operation of clutch C, an oil channel structure is adopted in which the boss section 102 is provided with a supply oil channel 101a in a radial direction, and an annular recessed groove 101b is formed in the outer peripheral surface of the boss section at the tip of the oil channel, and the hub 103 is formed with a slanted oil channel 107 for communication between the annular recessed groove 101b and the hydraulic actuator 105.
Recently, as shown in Japanese Patent Application laid open under No. 62-93546 filed by the same applicant as the present application, an automatic transmission is disclosed wherein an automatic transmission is provided to have a first automatic transmission mechanism section comprising a gear unit positioned on an input shaft and having a single planetary gear and a dual planetary gear in combination, and a second automatic transmission mechanism section (additional transmission section) positioned on a counter shaft and provided with under-drive and direct connection.
In the automatic transmission, the second automatic transmission mechanism section has an oil channel structure in which the boss section is provided with an annular recessed groove and the hub is provided with a slanted oil channel.
Incidentally, in the oil channel structure as mentioned above, the hub must be provided with a slanted oil channel section therethrough, and a seal groove must be provided on the left and right sides of the annular recessed groove of the boss section corresponding to the slanted oil channel section, by which the hub must be extended, resulting in a cause of its larger axial size.
In operation, in the F.F. automatic transmission, if a third speed automatic transmission mechanism is used in the first automatic transmission mechanism section, the axial size of the counter shaft becomes relatively significant, therefore reduction in the axial size is required in the counter shaft in an upper portion of the automatic transmission where there are many limitations in the setting space due to the existence of side frames and so on.